Cadmium (Cd) and zinc (Zn) toxicity in Enchytraeus doerjesi after 28-day exposure experiments was studied at 15, 20, and 25 °C. Cd lethal concentration (LC)(50) decreased with increasing temperature (293.01 mg kg(-1) at 15 °C, 261.62 mg kg(-1) at 20 °C, 231.79 mg kg(-1) at 25 °C). In contrast, Zn LC(50) increased with increasing temperature (420.21 mg kg(-1) at 15 °C and 518.42 mg kg(-1) at 20 °C). At 25 °C, a Zn LC50 could not be computed owing to the lack of sufficient adult mortality (LC(50) > 640 mg kg(-1)). The reproductive output at 20 and 25 °C was similar for each metal. Cd EC(50) for reproduction increased between 15 and 20 °C (from 23.93 to 35.11 mg kg(-1)) and decreased between 20 °C and 25 °C (to 16.84 mg/kg). Zn EC(50) increased dramatically from 15 °C (41.47 mg kg(-1)) to 20 °C (111.75 mg kg(-1)), and then slightly from 20 °C to 25 °C (112.17 mg kg(-1)). This indicated that metal-temperature effects on E. doerjesi may vary depending on the endpoint. The deleterious effects of Cd on the survival of E. doerjesi increased steadily with increasing temperature. With regard to reproduction, Cd toxicity could be exacerbated by extreme temperatures (15 and 25 °C) although conflicting pressures between high temperature and Cd toxicity may have prevented higher reproduction beyond 20 °C. The effects of Zn toxicity on survival decreased consistently with increasing temperature. The marginal increase in Zn EC(50) between 20 and 25 °C may explain the lack of a significant change in reproduction between the two temperatures. Energy redistribution between the below organism and higher organization endpoints in response to metal contamination may further explain these results.
Keywords: cadmium; enchytraeid; reproduction; survival; zinc.
Copyright © 2012 John Wiley & Sons, Ltd.